Here’s where immigration controls in liberal democracies and apartheid in South Africa after 1948 share some similarities. In both cases the effectiveness of the policies depends in the end on controlling not just outsiders but also insiders – citizens and residents. It is widely assumed that immigration control is a matter of keeping people from entering a country, and the rhetoric of control encourages this impression. Cities, public facilities, and social services are routinely described as bursting at the seams or stretched to the limit, unable to cope with sudden influxes of large numbers of foreigners, or the growth of a population swelling steadily because of a positive rate of net migration.

And:

This was the logic of Apartheid. Controlling who could enter from the bantustans required controlling the movement of black people within white society. The so-called ‘pass laws’ that first appeared in the nineteenth century to limit and control the movement of black labour, were extended to require both male and female Africans to carry ‘reference books’ detailing among other things, employment record, marital status, taxes paid, and official place of residence—and failure to carry the ‘dompas’ eventually became a criminal offence punishable by a prison sentence. By 1970 not only Blacks but also Whites, Coloureds and Asians were issued with (though not all were obliged to carry) similar documents under the Population Registration Amendment Act. Even when it is possible to identify some people readily, by skin colour or other other visible characteristics, it is not easy to control them without controlling others.

Indeed. A classic case of how a perverse policy corrupts all that is around it. Once you criminalize movement, you criminalize employers, landlords, and schools who might wish to interact with immigrants. But Kukathas holds back from a more fundamental comparison. Both apartheid and border controls are essentially forms of social control aimed at outsiders. In apartheid, the division is racial. For border controls, it is both national and racial, in that the harshest regulations are aimed at low status ethnic groups (e.g., Mexican laborers are more likely to be raided than college students whose visas are expired).